BACKGROUNDGroundwater is the primary drinking water source in the alluvial-pluvial fan of the Hutuo River. Pesticides application during agricultural planting leads to groundwater pollution. The pesticide pollution investigation work of this area in groundwater is relatively scarce.

OBJECTIVESTo study the pollution and distribution characteristics of pesticides in groundwater collected in the alluvial-pluvial fan of the Hutuo River.

METHODSGas Chromatography-Mass Spectrometry was used to analyze 75 pesticides in 30 groups of groundwater samples, and the results were investigated by statistical methods.

RESULTSThe results show that pesticides were detected in all 30 sampling sites. 40 of 75 pesticides were detected, which include organochlorine pesticides, organophosphorus pesticides, and organic nitrogen pesticides. The pesticides with the highest detection frequency were 3-hydroxycarburan (93.3%), dioxathion (90.0%) and chloroneb (90.0%). The pesticide with the maximum sum detection concentration of 30 samples was carbofuran (4860.6ng/L). The average detected concentrations of three pesticide types in the study area were 70.8ng/L for organochlorine pesticides, 392.7ng/L for organophosphorus pesticides, and 580.9ng/L for organic nitrogen pesti-cides, which is related to the application history and property of three pesticide types.

CONCLUSIONSOrganochlorine pesticides were banned in 1983 due to their high toxicity and hard degradation. At the beginning of the 21st century, relatively efficient and easily degradable organophosphorus pesticides and organic nitrogen pesticides developed rapidly. From the top to the middle of the alluvial fan, the concentration of the three pesticide types decreased gradually. The spatial distribution characteristics of pesticides were mainly influenced by the hydrogeological characteristics of the alluvial fan. HCHs in the area were from the recent using of lindan or industrial degradation of HCHs, DDTs were from the release of new DDT or historical ultilization. The research results provide basic data support for groundwater pesticides pollution monitoring and groundwater-related standard formulation in China.